FDTD Method Applied To Analyzing Frequency Selective Surfaces

A frequency selective surface (FSS) is a metallic periodic structure with frequency selective properties. Depending upon design, it may be low-pass, high-pass, band-pass, band-stop filter. Two important applications are as band-pass radomes and as sub reflectors for dual frequency reflector antenna system. During recent years, FSS have been used over a wide range of frequencies, from microwave to light wave, and have proved useful in nation defence works. FSS's frequency characteristic is a function of its cells form, measure, and array parameter etc. At the same time, dielectric substrate influence frequency characteristic as well. So design of FSS is very difficult. FSS of analysis and computing is significant. The traditional method of FSS of analysis is integral equation method, field component match method etc. but analytic process is very complex and confused. In order to reduce analytic complex, the new arithmetic are development in recently years. Such as Finite Element Method (FEM) and Finite Difference Time Domain (FDTD). FDTD is direct time domain method for solving Maxwell's equations.In this thesis, author briefly introduces basic theory of FDTD method at first, and research the method for analysing FSS: The finite difference time domain combined with periodic boundary condition (PBC) and absorber boundary condition (ABC) becomes the accurate andefficient tools for analysing Frequency Selective Surfaces. Using Field Transformation ideas and Split-Field method to solve the difficulty of setting periodic boundary condition when excitation is abnormally incident, and founding time domain function for analysis of FSS. Using the function above, author have finished double concentric loop, tri-slot, ring, and convoluted-double-square FSS flat plate samples, discussed the computed results and in accord with other relational article.